Section of the Lower Greensand at Atherfield. 225 



The author having been present during the reading of Mr. Aus- 

 ten's paper " On the South-cast of Surrey," on the 5th ultimo, 

 stated verbally his belief that the deposits which that gentleman there 

 proposes to distinguish as the " argillaceous or Neocomian " division 

 of the subcretaceous series, must be the same as that which he himself 

 had described*, as constituting the lowest portion of the lower green- 

 sand at Atherfield, in the Isle of Wight : but not having seen the 

 place for more than sixteen years (1826), and at a time when the 

 section was in a great part concealed by masses of ruin, he was 

 desirous of examiniug it again. This paper contains an account of 

 what he has recently observed there. 



The time of the author's late visit to Atherfield was very fortu- 

 nate ; the sea, during severe gales having previously cleared away, 

 not only a great part of the ruin which formerly concealed the base 

 of the cliffs, but having entirely removed the shingle of the beach 

 to a most unusual extent ; so that the junction of the Wealden with 

 the lower greensand was distinctly exposed for several hundred yards, 

 while a very large surface of the adjacent strata, washed perfectly 

 clean, was visible at low water, on both sides of it. 



§_ The strata composing the section thus beautifully exhibited, 

 were the following : — 



i . Weald clay, with the usual characters ; which it is not the object 

 of this paper to describe in detail. The very uppermost beds here 

 consist of slaty clay, and contain some characteristic fossils of the 

 Wealden, especially Cyclas media, and small Paludince ; and along 

 with these, at the top of the freshwater strata, were Cerithia, probably 

 of a new species, with one or more thin-shelled oysters or Gryphcete 

 in comparatively smaller number. These fossils occur within a very 

 few inches from the junction with the sand above the Wealden ; so 

 that it would be possible, with care, to obtain portable masses, in- 

 cluding both the Weald clay with its characteristic species, and 

 part also of the incumbent mass with its marine shells. 



2. The junction, which here occupies not more than six or eight 

 inches in vertical thickness, is formed by an alternation or interjec- 

 tion of greenish -grey fine sand among slips or slices of the dark Weal- 

 den shale. The lowest portion of the next bed (3) which rests upon 

 this sand includes a large quantity of a kind of gravel, containing 

 numerous fragments of fish-bones. 



3. The beds immediately above the sand at the junction (2), con- 

 sist of a tough, greenish mudlike mass, which becomes grey in 

 drying, and seems to be an intimate mixture of clay and sand. It 

 is not more than from 1\ to 3 feet in thickness ; and at the top it is 

 very closely connected with the lower part of the indurated stratum 

 (4) : but after exposure even for a short time to the air and sea, the 

 soft matter of (3) is rapidly removed, leaving the firm mass of (4) 

 detached and prominent ; and this being undermined, appears upon 

 the shore in rudely quadrangular detached blocks. 



The fossils of the lowest clay (3) appear to be the same, though the 

 species are less numerous, with those of (4) above it. The most re- 

 * Geol. Trans., 2nd Ser. vol. iv. p. J96, &c» 



Phil. Mag. S. 3. Vol. 24. No. 1 58. March 1 844. Q 



